The goal of this study is to investigate the role of Eph A receptor protein tyrosine kinases (RPTK) and their ligands (ephrins) in producing a non- permissive environment for axonal regeneration after spinal cord injury (SCI). Molecular biology, protein biochemistry, neuroimaging tracing strategies and behavioral assays will be used in conjunction with injured rats at the T10 level to analyze the expression of these proteins. The first aim will focus on the spatial and temporal expression of Eph A and ephrin A, mRNAs and proteins, after spinal after Central Nervous System (CNS) lesion at the nuclei and amino acid level. The expression pattern will moderate spinal cord contusion, In the second aim, we will determine the possible role of Eph A RPTK and ephrins as repulsive molecular cues that restrict axonal regeneration and functional recovery after SCI. For this study, fusion proteins expressing the amino terminus of the Eph A RPTKs or ephrins A will be temporal and spatial expression of individual Eph A RPTKs and ephrins, both on the regenerating fibers and in the local environment, may lead to novel therapeutic strategies to enhanced regeneration and functional recovery after SCI.